Some one please help me I need return this test this night.

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.

Write the standard form of an equation with (see picture below)

In a tutoring session, 2/3 of an hour was spent reviewing math problems. adelina attended 3/4 of the tutoring session. how much time did adelina spend at the tutoring session?